Seismic methods for locating underground discontinuities are well known, which methods often include the generation of seismic waves at one location and the detection of refracted or reflected seismic waves from the discontinuity at the same or different locations. However, few prior art seismic methods are suitable for locating underground chambers, caves, covered pits, rooms, tunnels, tubes, or the like, and it is possible that many sites of archeological interest have eluded discovery using such conventional seismic exploration techniques. A method for locating tunnels, or the like, is shown in U.S. Pat. No. 3,836,952 wherein continuous waves are transmitted and deviations in the phase angle difference between the transmitted and received waves as the span between the transmitting and receiving transducers is displaced or changed are taken as indicative of a tunnel, or the like. Heretofor, measurements of the amount of acoustic wave energy transmitted to receiving sites from a transmitting site, from which measurements energy differences are taken as being indicative of subterranean discontinuities, have not been employed for mapping of faults, underground chambers, and the like.